Power transmitting device



5 Sheets-Sheet l C. J. WERNER POWER TRANSMITTING DEVICE Filed Dec.

' Aug. 28, 1945.

M m 2 4 N ma E Aug. 28, 19. c. J. WERNER POWER TRANSMiTTING DEVIC E 3Sheets-Sheet 2 Filed Dec. 10, 1942 m \(E'NTOR V cm vm J WERNER BY I aHA5 HTTORNEYS Aug. 28, 1945. c. .J. WERNER 93 9 POWER TRANSMITTINGDEVICE Filed Dec. 10, 1942 3 Sheets-Sheet 3 Ira/1mm 2 W VE/Y TOR 04.4'w/y J. Ween E2 flaw W 5 m5 AWTORNE Y5- it P a tented Aug. 28, 1945POWER TRANSMITTING DEVICE Calvin J. Werner, Dayton, Ohio, assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareApplication December 10, 1942, Serial No. 468,475

14 Claims.

This invention relates to improvements in load supporting devices suchas jacks or the like and which are adapted to exert a pushing or pullingeffort as the-device is extended or retracted.

It is among the objects of the present invention to provide a unitarypower driven load supporting device of compact and sturdy constructioncapable of exerting a powerful, smooth and steady pushing or pullingeffort as the device is actuated in one direction or the other to movethe load.

A further object of the present invention is to provide a power actuatedload supporting device capable of being brought to a substantiallyabrupt stop upon reaching a predetermined point in its extending rretracting movements.

It is a still further object of the present invention to provide a poweractuated load supporting device with a manually operable means adaptedto actuate the device to perform its function in case of failure of thepower device.

In existing devices of the kind illustrated in the present invention thesource of power such as a hand crank, motor or the like is remote fromthe relatively movable extending and retracting members thus requiringthe useof levers, shafts or cables for connecting the source of powerwith the extending and retracting members. A load supporting devicecomprising a hand crank or motor, a plurality of levers, shafts andcables and the extending and retracting members makes for a heavy andcumbersome assembly which requires considerable space and necessitatessubstantial time for its installation. This is particularly undesirableand actually prohibitive when a device of this kind is to be installedin an airplane for purposes of raising and lowering the landing gear,for in an airplane weight is a most important factor and space is at apremium.

The present power actuated load supporting device is a light weight andcompact structure, which, when used as a landing gear operating device,actually forms one of landing gear assembly thereby requiring nomultiplicity of shafts, levers or chains which add weight and increaseassembling time both of which are appreciably reduced by the presentdevice.

In addition to its lightness, compactness and sturdiness, other objectsand advantages of the present invention will be apparent from thefollowing description, reference being had to the accompanying drawings,wherein a preferred embodiment of the invention is clearly shown.

In the drawings: 1

the struts of the Fig. 3 is a full size sectional view of the other(lower) portion of the device.

Fig. 4 is a cross section taken along the line. 6-6 of Fig. 3. r

Fig. 5 is a detail, part sectional view of the sleeve-nut.

Fig. 6 is a schematic view of a lowered airplane landing gear equippedwith the present invention.

Fig. 7 is a view similar to Fig. 6, however, showing the landing gear inretracted position.

Fig. 8 is a wiring diagram showing the various electrical elements andtheir-circuit connections.

Referring 'to' the drawings, the numeral 2c designates the electricmotor as a whole. The motor comprises a casing 2i and cover 22. Cover 22supports a bearing 23 in which one end of shaft 26 of motor armature 25is journalled. The other end of shaft 24 is jpurnalled in a bearing 25carried by the housing 30' which is recessed to receive and support oneend-of the motor casing H. The numeralsZlU and 27D designate the fieldwindings of the electric motor 20 which are secured in the casing H inany suitable manner. The pole pieces of the electric motor aredesignated by the numerals 29. To simplify the drawings no brushconstruction cooperating with the commutator: 29 of the armature 25 hasbeen shown. Suiiice to say that any standard brush mechanism can beused, said brush mechanism being carried by the cover 22 in any suitablemanner.

Thehousing 39, as shown in Fig. 1, has lugs on oppositely disposed sidesthereof, said lugs each being bored out and threaded as at 3|. Thesethreaded lugs receive bolts for attaching the forked end of a mountingbracket 32 to the housing 3| as shown in Figs. 6 and -7. The mountingbrackettiis hingedly secured on a stud 33 attached to the fuselage 34 ofthe airplane, only a fragment of the fuselage 38 being shown in Figs. 6and 7.

Fig. 2 clearly illustrates the housing and its contents. At the end ofhousing 30 adjacent the electric motor 20 an end wall 35 is centrallybored to housethe bearing 28 which, as has been described, supports thearmature shaft 24. This end of'housing 30 is recessed to receive the endof the electric motor casing 2| which is secured to the housing bybolts." (Fig. 1). The other end of housing 30 is providedwith a screwcap 31 locked in proper position on the housing by the finger 30attached to housing 90 by bolt 39. The screw cap 39 has a centralopening 49 through which extends the body portion 4| of the screw-shaft42. An enlarged head portion 49 on screw-shaft 42 is rotatably supportedwithin the housing 90 by two sets of roller bearings, one on each sideof an annular flange 44 provided on the shaft head 43. The one set ofroller bearings 49 are interposed between the flange 44 and an endthrust bearing ring 40 resting upon the end-cup I1 and the set of rollerbearings 41 is interposed between flange 44 and an end thrust ring 40fixedly positioned in the housing 30. This ring 49 has its innerperiphery provided with gear teeth 49 forming an internal ring gear forthe speed reduction gearing of the device.

The shaft head 43 is recessed as at 80 and in this recessed head thereare provided internal gear teeth forming another internal ring gear forthesaid reduction gearing. A counter bore in recess 00 houses the rollerbearing 02 in which is supported one end 03 of the speed reductiongearing shaft so that this portion 09 of the shaft is concentric withthe ring gears 49 and II. A counter-balance weight member 04 is securedto shaft portion 53 adjacent bearingil'.- The other end 55 of thegearing shaft is iournalled in ball bearing 00 carried in a centralrecess provided in the cup-shaped partition member. 51 whichfits withinthe housing 30 and rests upon the end thrust ring 40 to hold it inposition. A balance weight is secured to this portion 50 of the gearingshaft. Between'its portions 50 and 55 which are concentric, the gearingshaft has an eccentric portion 60 lying within the confines of the twomensions of cooperating gears Bi-49 and B25I are predetermined toprovide a selected speed reduction which may readily be altered byvariations in the relative sizes of these cooperating I gears.

The end of shaft portion 55. is centrally recessed as at I0 and flatportions II are provided in the peripheral surface adjacent this end. Anarmature disc 12 of magnetizable metal is centrally recessed to fit overand on the partially flattened end of shaft portion 55 so that disc Handshaft portion 55 must rotate together, however, disc 12 may slidelongitudinally on said shaft portion 55', A cup-shaped spring retainer74 has its open end attached to the armature disc 12 and extends intothe recess 10in shaft portion 55, A headed screw I5 is threadedlysecured in the shaft portion 55 so that the screw passes concentricallyinto the spring retainer I4. A spring I6 is interposed between thebottom of the spring retainer 14 and the head of screw 15 and normallyurges the armature disc I2 into gripping engagement with a brake ring 80made of any suitable friction material and resting upon the outersurface of the partition member 51. A spacer collar 8| fits slightlycounter-bored to fit over brake ring 49 and thus clamp and hold itagainst movement upon the partition member 01. The disc 93 has aninwardly extending annular flange 94 at and coaxial with its centralopening in which the hub portion of a driving disc 90, secured to theshaft 24 of the motor armature 29, may rotate. A ring 96 in the spacercollar II supports a magnet winding 99 within the annular space definedby the collar II, disc 89 and its annular flange portion 94 and ring 08.The space between the hub of driving disc 90 and flange portion 94 issuch that a good magnetic field can be established by the energizationof winding 99.

The inner face of the end ring 31 is counterbored to receive the annularflange 90 on a flexible and collapsible sealing sleeve 9|. A retainerring 92 fits over the annular flange portion 90 of the sealing sleeve 9|being urged to hold said flange portion 90 in position in the recess ofend ring 31 by the head portion 49 of the screw-shaft 42 which engagessaid retainer ring 92.

Figs. 3, 4 and 5 illustrate the lower end portion of the forcetransmitting device and the following description will have referencethereto.

The numeral I 00 designates a helical groove provided in the screw-shaft4|. This groove is formed in the shaft from near its head portion 4| tothe extreme outer end. A traveling nut in the form of a sleeve IOI fitscomparatively loosely about the grooved shaft, said sleeve having ahellcal groove I02 provided in its inner peripheral surface,corresponding in size and pitch to the helical groove I00 in the outerperipheral surface of the shaft. An outwardly extendin flange is formedat each end of the sleeve IN, the one flange being numbered I03, theother 504. Another outwardly extending flange I05 is formed on thesleeve intermediate its flanges I03 and I04. This intermediate flange105 has spiral gear teeth I06 cut in its outer peripheral surface.

Two spaced apertures I01 and I08 are provided in the annular wall of thesleeve IOI between flanges I03 and I05 and two similar apertures I09 andH0 are provided in the sleeve IOI between flanges I04 and I05. All ofthese apertures are so arranged that they lead directly into andcommunicate with the helical groove I02 within the sleeve IN. A tube IIIis bent to conform substantially to the contour of the sleeve IIII, oneend of the tube extending into the aperture I01, the other end into theaperture I08, thereby providing outside and shunting communicationwithin the housing 30 and is interposed between 9 between spacedportions of the helical channel formed by the contiguous and coincidinggrooves I00 and I02 of the shaft 4! and sleeve IOI respectively. Asimilar tube H2, shown in section in Fig. 5, provides communicationbetween apertures I09 and I I0 in sleeve I05 and likewise forms anoutside shunting passage which is in communication with the helicalchannel at spaced points. Tube III is secured to the sleeve IN by a clipII 3 screwed to the sleeve and a similar clip II4 attaches the tube II2to the sleeve in a like manner. A series of balls I I5 fills the tube III and that portion of the helical channel between sleeve apertures I01and I08 and a series of similar balls H6 fills the tube H2 and theportion of the helical channel between apertures I09 and H0 in thesleeve IOI. These balls mechanically connect the sleeve IOI- to theshaft 4| so that rotation of either one relatively to the other willcause a relative longitudinal movement between said sleeve and shaft.The result is the same as having ordinary cooperating screw threads onthe sleeve and shaft, however, by using the balls in the helical channelformed by the coinciding grooves in the Sleeve and shaft, friction isreduced to a minimum and strength greatly increased.

The traveling nut or sleeve IOI is rotatably supported within a casingI50, the flanges I03 and I04 fitting into said casing so as to providebearings for the sleeve as it rotates in the casing. An apertured bottomend wall I5I of the casing has an inner end thrust bearing ring I52engaged by the flange I04 of the sleeve IN. A similar end thrust bearingI53 is engaged by the flange I03 of sleeve IOI, this bearing I53 beingheld in engagement with said flange I03 by a centrally apertured screwcover I54 at the end of the casing I50. This screw cover I54 has anannular groove I55 which receives the annularly flanged end I55 of theflexible and collapsible sealing sleeve 9|. A metal ring I51 in saidflange I56 provides means for anchoring the sealing sleeve to the screwcover I54.

A sealing sleeve I60, similar to sleeve 9| is provided at the other endof easing I50. One end of this sleeve I60 is secured to casing I50 by aclamping ring I6I attached to the casing by screws I62. The other end ofsealing sleeve I60 is anchored to a stud I63 secured in the end of thescrew shaft 4 I.

As shown in Fig. 4, the casing I50 has an extension I10 in which twoaligned bearings HI and I12 are supported. In these bearings isjournalled a shaft I14 providing a spiral pinion I15 which meshes withthe spiral gear teeth I06 provided in the peripheral surface of theflange I05 on sleeve-nut IOI. Shaft I14 is connected to any suitablehand operating device such as a crank or wheel (not shown) by a flexibledrive I11 shown in the schematic views Figs. 6 and '1. Two diametricallyopposite lugs I80 and I8I are provided on casing I50 and form means towhich struts are secured. When installed, the casing I50 cannot rotate,but it may move lengthwise of the screw-shaft 4|. Due to thenon-rotatability of easing I50 in installation, sleeve-nut IOI will notrotate when screw-shaft 4I turns, for the engagement of spiral pinionI15 carried by the casing I50 with the spiral gear teeth I06 in theflange I05 of the sleeve-nut whereby said casing and sleeve-nut arelocked together. However, when the spiral pinion is manually turned itwill turn the sleeve-nut IOI relatively to the casing I50 andscrew-shaft M and thus cause the sleevenut and casing to move lengthwiseon the screwshaft.

The Figs. 6 and 7 schematically show the present device installed in anairplane landing gear. The wheel of the landing gear is designated bythe numeral 200. The spindle or axle I of said wheel is secured in themember 202 of the shock absorbing strut 203 which is hingedly attachedto the stud 204 mounted on the fuselage 34 of the airplane. The member202, which is the iongitudinallymovable part of the shock absorbingstrut 203, has a protruding lug 205 to which is pivotally secured oneend of a strut link 206, the other end of said link being hingedlysecured to the lug I8I of the sleeve-nut casing I50. One end of a strut201 is also hingedly secured to said lug I8I, the other end of strut 201being pivotally attached to the fuselage 34 by stud 208.

Reference to Fig. 6, which illustrates the landing gear loweredpreparatory to the landing of the airplane, shows that during thelanding, horiby the shock absorbing strut 203. No stresses of anyappreciable degree are directed against the operating strut includingthe screw-shaft 4I, sleeve nut IOI, housing 30 and mounting bracket 32.The Fig. 7 illustrates the landing gear retracted and folded up into thefuselage 34.

The Fig. 8 shows the various electrical elements and their circuitconnections. The motor 20 is grounded. It has two field windings 21U and21D connected in series with the electromagnet winding 88. Field winding21U is connected to a stationary contact 2I0 of a magnet switch, theother fleld winding 21D being connected to a stationary contact 2 ofanother magnet switch. I

The other stationary contacts 2I2 and 2I3 of the two magnet switches areconnected together at the point 2I4 which is connected to one side ofthe storage battery or source of electrical power 2I5 and also to theoperating contact arm 2I6 of a manwually operable selector switch 2I1.The storage battery is grounded on one side as shown.

Contacts 2I0 and 2I2 of the one magnet switch are adapted to be bridgedby the movable contact 2I8 which is adapted to be moved into itsbridging position by the energization of the magnet winding 2I9, one endof which is connected to the grounded side of the battery, the other endbeing connected to the one stationary contact 220 of the strut operatedswitch MI. The other stationary contact 222 of switch 22I is connectedto the up contact 223 of the selector switch 2I1. The movable contact224 of switch 22I is adapted to be actuated by the bracket 32 when thelanding gear has reached a certain point in its retracting movement.Contacts 2H and 2 I 3 are adapted to be bridged by the movable contact225 and when the magnet coil 226 is energized by the closing of switch322. One end of coil 226 is connected to the grounded side of thebattery, the other end to the stationary contact 221 of switch 322, theother stationary contact 228 of which is connected to the down contact229 of selector switch 2I1, illustrated as engaged by the movable arm2I6 of this switch. The movable bridging contact 230 of switch 322 isalso adapted to be controlled by the bracket 32, being opened when thebracket is in its landing gear lowered position and closed when thelanding gear is in its retracted or raised position.

During flight the landing gear of the airplane is in the position asshown in Fig. 7. When the pilot decides to land he moves the arm ormovable contact 2I6 of the selector switch 2I1 into the down position asshown in Fig. 8. Now current from the battery 2I5 flows across movablecontact 2I6 engaging down contact 229 of switch 2I1 to contact 228 ofclosed switch 322, then through contacts 230 and 221 of said switch,magnet winding 22B and back to the opposite side of the battery 2I5.This will cause energization of the magnet having winding 226 causingthe movement of contact 225 to bridge contacts 2 and 2I3. This closesthe circuit including battery 2I5, point 2I4, contacts 2I3, 225 and 2,motor field winding 21D, electromagnet winding 88 and through motor 20back to the battery via ground, resulting in the energization of theelectromagnet winding 88 which causes the armature disc 12 to beattracted and moved into driven engagement with the motor driving disc85. It also causes the operation of the electric motor in one direction,specifically in the direction in which the screw-shaft 4I, driven by themotor through the driving disc and reduction gearing in housing 30 willcause the sleeve-nut ill, to move downwardly on said screw-shaft. As thesleeve-nut llll moves downwardly along .the screw-shaft 4| the casingI50 enclosing it will likewise move (to the right as regards Fig. 7)thus moving strut 201 about its pivot stud 20!. causing a downward forceto be exerted through link strut 208 and thereby lowering the wheel 2".When the landing gear reaches its lowered position the bracket 32thereof will engage and open switch 322, breaking the circuit throughthe magnet winding 226 and by its consequent deenergization causing thedisengagement of switch contacts 2| I and 213 by contact 225. Now themotor circuit is broken and the motor ceases to operate and also theelectro-magnet winding '2 is deenergized thereby permitting the springIi to move the armature disc 12 out of driven engagement with the motordriving disc 86 and into engagement with the braking ring 80. Thefrictional engagement of armature disc 12 with braking ring 80 quicklystops rotation of the speed reduction gearing connected to the screwshaft ll.

.220 and 222 in anticipation to the landing gear raising or retractingcycle which is effective by the operation of the selector switch arm orcontact 2|6 into engagement with the "up" contact 223. When this is donethe electromagnet winding 2|! is energized causing closure of contactsH0, H2 and 2l8 to energize the motor winding 2IU and electromagnetwinding 88 resulting in the operation of the electric motor in theopposite direction. This motor operation turns the screw shaft H to movethe sleeve-nut IBI upwardly drawing the casing I50 and its attachedstruts 206 and 201 toward housing 30 and finally pulling the wheel 200from the position shown in Fig. 6 to the position shown in Fig. 7. Asthe landing gear so moves, switch 322 will be closed and switch 22iopened preparatory to the landing gear lowering operation.

Dust, dirt and moisture are prevented from reaching the operating partsand particularly the screw-shaft 4| of the device by the sealing sleevesii and I80 which are contracted and expanded as the casing ISO is movedback and forth along the said screw shaft.

If; forany reason there is a failure in the electrical system so thatthe motor cannot be used to actuate the screw-shaft or a failure in thedriving connection so that the screw-shaft itself cannot be rotated,then manual means such as a crank or wheel, connected to a flexibledriving member ill may be used to turn the spiral pinion which willrotate the sleeve-nut IOI relatively to the stationary screw-shaft llresulting in the necessary travel of said sleeve-nut and its-casing I50along the screw-shaft ll.

;;.'f'rom the aforegoing description it is shown that the presentinvention provides a light, sturdy and compact, unitary load supportingdevice driven by an electric motor. The device is so designed that theelectric motor or power source forms a part of the unitary assembly andactually moves therewith. This facilitates and reduces time forinstallation and also eliminates the necessity of numerous and sometimeslong rods, levers or chains necessary for transmitting movement wherethe power or moving source is remote from the member to be actuated.

aseacor While the embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted. all coming within the scope of the claimswhich follow.

What is claimed is as follows:

1. In combination with a main body having a load movably attachedthereto, of an extensible and retractible load moving device comprising.a screw having a nut threaded thereon; a

member attaching the nut to the load; an electric motor for rotating thescrew; means securing the electric motor to the main body; means forpreventing rotation of the nut while the screw is being rotated by theelectric motor; means for rotating the nut; and means for preventing'rotation of the screw while the nut is being rotated.

2. In combination with a main body, of a load movably supported thereby,an extensible and retractible load moving device comprising, a screwhaving a nut threaded thereon; means for ate taching the nut to theload; an electric motor operatively connected to the screw for rotatingit; means for attaching the electric motor to the main body; means forlocking the nut against rotation while the screw is being rotated by theelectric motor, said means being manually operable to rotate the nut onthe screw; and means for locking the screw against rotation when the nutis being manually rotated.

3. In combination with a main body, of a load suspended therefrom, anextensible and retractible load moving device interposed between thebody and load comprising, a screw having a nut threaded thereon; atrunnion securing the nut to the load; an electric motor pivotallyattached'to the main body and operatively connectible to the screw forrotating it; means for connecting the electric motor with the screw whensaid motor is energized; means operatively engaging the nut to hold itagainst rotation while the screw is being rotated by the electric motor;manually operable mechanism for rotating said last mentioned means toturn the nut on the screw; and means for locking the screw againstrotation while the nut is being rotated. I

4. In combination with two relatively movable elements, one a body, theother a load movabiy secured to said body, an extensible and retractibleload moving device comprising, a screw having a nut threaded thereon;means anchoring the nut to one of said elements; an electric motoranchored to the other of said elements and operatively connectable tothe screw for rotating it; means connecting the motor with the screw;means operatively engaging the nut to lock it against rotation while thescrew is being rotated by the motor; manually operable mechanismconnected to the last mentioned means for rotating it to turn the nut onthe screw; and means for locking the screw against rotation while thenut is being operated manually.

' 5. In combination with a body; of a load movably attached thereto; anextensible and retractible load moving device comprising, a screw; a nutthreadedly mounted upon said screw, said nut having gear teeth providedabout its outer periphery; a. trunnion for securing the nut to the load;an electric motor for rotating the screw; means pivotally securing theelectric motor to the body; a pinion rotatably carried by the trunnionand meshing with the gear teeth on the nut, said pinion locking the nutagainst rotation when the screw is rotated by the motor; meansfor'rotating the pinion to turn the nut on the screw; and means forlocking the screw against rotation while the nut is being turned by thepinion.

6. In combination with a body; of a load movably attached thereto; anextensible and retractible load supporting device comprising, a screw; anut threadedly mounted upon said screw, said nut having gear teethprovided about its outer periphery; a housing attached to the body androtatably supporting the screw; a second housing attached to the loadand rotatably supporting the nut; an electric motor carried by the firsthousing for rotating the screw; means rotatably supported in the secondhousing and operatively connected to the nut for looking it againstrotation while the screw is being rotated by the motor; means forrotating the first mentioned means to turn the nut relatively to thescrew; and means for holding the screw against rotation while the motoris inoperative.

7. In combination with a main body; a load movably attached to saidbody; an extensible and retractible load moving device comprising, ascrew; a nut threaded thereon; separate housings rotatably supportingthe screw and the nut respectively; means pivotally attaching saidhousing to the body and the load respectively;

an electric motor on the housing of the screw,

a braking member secured in the housing of the screw; a disc operativelyconnected to the screw, normally engaging the braking member to preventrotation of the screw; means, rendered effective when the electric motoris rendered operative, for moving and disconnecting the disc from thebrake and operatively connecting said disc with the electric motor;means in the housing containing the nut, operatively engaging the nut tolock it against rotation when the screw is being operated by the motor;and manually operable means for turning said locking means to rotate thenut relatively to the screw when the motor is inoperative.

8. In a device of the character described the combination with a body;of a load movably secured to the body; an extensible and retractibleload moving device comprising, a pair of housings each one of which isadapted to be secured to the body, the other to the load; a screwextending from and rotatably supported by one of said housings; a nut onthe screw, rotatably carried by the second of said housings; an electricmotor on the said one housing for driving the screw; means in the saidsecond housing, engaging the nut to lock it against rotation while themotoris driving the screw, said means being rotatable in its housing toturn the nut relatively to the screw; and means in the said one housingfor holding the screw against rotation while the electric motor isinoperative.

9. In a device of the character described, the combination with a mainbody; of a load movably supported thereby; an extensible and retractibleload moving device comprising, a pair of housings one of which ispivotally secured to the main body, the other being pivotally anchoredto the load; a screw rotatably supported by and extending from one ofsaid housings; a nut threadedly engaging the screw and rotatablysupported in the second housing, said nut having an outer, annularflange providing a gear; an electric motor on the first housing adapted,only when energized, to be connected to the screw for driving it; anelectromagnet clutch for connecting the motor with the screw; a pinioncarried in the second housing and meshing with the gear on the nut, saidpinion normally holding the nut locked to the housing but adapted to berotated relatively to the housing to turn the nut on the screw; meansfor rotating the pinion; and means in the first housing engaged by aportion of the electromagnetic clutch for holding the screw againstrotation when said clutch is deenergized and the screw is disconnectedfrom the motor.

10. In a device of the character described, the combination with a mainbody; a load movably secured thereto; an extensible and retractible loadmoving device comprising, two separate housings one of which ispivotally attached to the body, the other to the load; a screw shaftrotatably supported by and extending from the one of said housings; anut rotatably supported in the second housing and threadedly secured onthe screw shaft; an electric motor on the first housing, connectingmeans in said first housing operatively connected to the screw shaft andrendered eifective for connecting the electric motor with the screwshaft to rotate it only when the motor is energized, means in said firsthousing,

engaged by the connecting means,. for locking said screw shaft againstrotation when said connecting means is disconnected from the motor;means in the second housing for locking the nut against rotation, saidmeans being manually operable to rotate the nut relatively to the saidsecond housing and the screw shaft for eifecting movement of the nutlongitudinally of the screw shaft.

11. In a device of the character described, the combination with a body;of a, load movably attached thereto; an extensible and retractible loadmoving device interposed between the body and the load and comprising,two separate housings one of which is pivotally attached to the body,the other to the load; a screw shaft rotatably supported by andextending from the first of said housings; a nut rotatably supported inthe second housing and threadedly secured on the screw shaft; anelectric motor on the first housing, electromagnetic means in said firsthousing said means having a member rendered effective for connecting theelectric motor with the screw shaft only when the motor is energized,braking means in said first housing, engaged by the said member of theelectromagnetic means, for locking said screw shaft against rotationwhen said member is disconnected from the motor; an outer, annularflange on the nut, providing a gear on said nut; a pinion rotatablysupported in the second housing and meshing with the gear on the nut,said pinion locking the nut against rotation with the screw shaft; andmeans for rotating the pinion to turn the nut relatively to the screwshaft and the second housing.

12. In a device of the character described, the combination with a mainbody; of a load movably secured thereto; an extensible and retractibleload moving device comprising, two housings adapted to be attached tothe load and body respectively;

a screw shaft rotatably carried by and extending from the one of saidhousings; an electric motor carried by said one housing; a brake elementcarried in said one housing, normally holding the screw shaft againstrotation; means responsive to the energization of the electric motor forconnecting the motor with the screw shaft to drive it: a nut in theother of said housings, threadedly mounted on the screw shaft and havingan exterior gear formed on its outer peripheral surface; a pinionrotatably mounted in the said other housing and meshing with the gear onthe nut to hold the nut against rotation when the screw shaft is drivenby the motor; and means posed between the motor and screw shaft forlocking the screw shaft against rotation when the motor is inoperativeand adapted to be energized concurrently with the electric motortoreiease the screw shaft lock and operatively connect it to' theelectric motor so that it may be rotated thereby; and a common means forholding the nut against rotation while the motor is operating and .forrotating the nut relatively to the screw.

shaft when said shaft is locked against rotation. 14. In a device of thecharacter described, the combination with a main body; a load movablysupported thereby; an expansible and retractible load moving devicecomprising two housings, one of which is pivotally secured to the mainbody. the other to the load; an electric motor in the said one housing;a screw shaft rotatably supportedpy and extending from, said onehousing; a nut rotatably supported in said other housing, said nutthreadediy receiving the screw shaft; speed reducing gearing in said onehousing and connected to the screw shaft; a braking member in said onehousing; a magnetic member operatively connected to the speed reducinggearing and yieldably urged into frictional engagement with the brakingmember; a magnetic driving disc secured to the motor so as to be rotatedthereby; a. magnet winding for energizing said driving disc to attractthe magnetic member, to move it out of engagement with the brakingmember and into engagement with the driving disc; a worm gear in thesaid other housing, operatively engaging the nut to hold it againstrotation while the screw shaft is being rotated, said worm gear beingadapted to rotate the nut relatively to the screw shaft while the motoris inoperative and the magnetic member frictionally engagesthe brakingmember.

CALVIN J. WERNER.

